Mothers wanting to give their children the best start in life can boost their intelligence simply by talking to them, a study has found.

Academics at Stanford University in California found kids' brains are much more engaged by their mother's voice than any other.

They discovered hearing mum speak triggers neurons involved in emotion and reward processing, social functioning, detection of what is personally relevant and face recognition.

And the brain activity triggered by her soothing tones could help predict the child's social communication skills - shedding fresh light on autism, said the researchers.

In the first study of its kind, psychiatrist Dr Daniel Abrams and colleagues used MRI scanners on 24 healthy seven to 12 year-olds as they listened to brief "nonsense words" spoken by their biological mothers and two unfamiliar females.

The mothers lit up a voice region called the STS (superior temporal sulcus) of the brain, the amygdala which is crucial for emotion, the nucleus accumbens and orbito-frontal cortex of the reward circuit and a face-processing region in the fusiform gyrus.

Moreover, children's social communication scores were predicted by the connections between the STS and brain regions involved in memory, emotion, face perception and reward-related function.

The children who responded most to their mothers' voice were better at communicating (file pic) (Image: Getty)

The study published, in Proceedings of the National Academy of Sciences, might help unravel social development and clinical disorders such as autism in which the perception of biologically important voices may be impaired.

Decades of research have shown children prefer their mother's voices: In one study one day-old babies sucked harder on a pacifier when they heard the sound of her voice as opposed to other women's.

Professor Vinod Menon said: "Nobody had really looked at the brain circuits that might be engaged.

"We wanted to know is it just auditory and voice-selective areas that respond differently, or is it more broad in terms of engagement, emotional reactivity and detection of salient stimuli?"

All the participants had IQs of at least 80, none had any developmental disorders and all were being raised by their biological mothers.

The research was carried out by academics at Stanford University (Image: Rex)

Parents answered a standard questionnaire about their child's ability to interact and relate with others.

And before the brain scans each child's mother was recorded saying three nonsense words.

Prof Menon said: "In this age range - where most children have good language skills - we didn't want to use words that had meaning because that would have engaged a whole different set of circuitry in the brain."

Two mothers whose children were not being studied - and who had never met anyone in the study - were also recorded saying the three nonsense words and used as controls.

Even from very short clips - less than a second long - the children could identify their own mothers' voices with greater than 97 percent accuracy.

Prof Menon said: "The extent of the regions that were engaged was really quite surprising.

"We know hearing mother's voice can be an important source of emotional comfort to children. Here we're showing the biological circuitry underlying that."

Children whose brains showed a stronger degree of connection between all these regions when hearing their mother's voice also had the strongest social communication ability.

This increased brain connectivity could be a neural fingerprint for greater social communication abilities in children.

Prof Menon said: "This is an important new template for investigating social communication deficits in children with disorders such as autism."

His researchers plan similar studies in children with autism. They are investigating how adolescents respond to their mother's voice to see whether the brain responses change as people mature into adulthood.

Prof Menon said: "Voice is one of the most important social communication cues. It's exciting to see the echo of one's mother's voice lives on in so many brain systems."